This disclosure relates primarily to the field of biological imaging, particularly to medical imaging. More specifically, to medical imaging equipment and methods for medical imaging using combined near-infrared optical tomography, fluorescent tomography and/or ultrasound.
Diffusive optical tomography (DOT) is a form of computer-generated tomography wherein near-infrared light (NIR) is directed at a inclusion (e.g., a lesion, a tumor, a cancer, and so forth) and the amount of light transmitted and/or diffused through the object, and/or reflected from the object, is detected and utilized to reconstruct a digital image of the target area (e.g., the object can exhibit a differential in transmission and/or diffusion from surrounding tissues). This method of imaging is of interest for several reasons, for example, differing soft tissues exhibit differing absorption, transmission and/or scattering of near-infrared light. Therefore, DOT is capable of differentiating optical properties between inclusions and normal soft tissues, wherein alternative tomography methods (e.g., Positron Emission Tomography, Magnetic Resonance Imaging, X-Ray, and so forth) cannot. Another example is that near-infrared light is non-ionizing to bodily tissues, and therefore patients can be subjected to repeated light illumination without harm. This in turn allows physicians to increase the frequency at which they monitor and/or track change in areas of interest (e.g., lesions, tumors, and so forth). Yet further, due to differences at which natural chromophores (e.g., oxygen-hemoglobin) adsorb light differently at different wavelengths, optical tomography is capable of supplying functional information such as hemoglobin concentration and oxygen saturation. For these reasons there is much interest in employing optical tomography for the detection and monitoring of cancerous tissues, especially in breast cancer applications.
Although diffusive optical tomography is a promising medical imaging technique, DOT imaging methods and DOT apparatus have yet to yield high quality reconstructions of inclusions due to fundamental issues with intense light scattering.
Another method of tomography imaging that is of interest is fluorescent diffusive optical tomography (FDOT). Fluorescent diffusive optical tomography is a form of computer-generated tomography wherein an excitation source (e.g., near-infrared light) is directed at an inclusion labeled by a fluorescence targets or dyes or fluorophores. Upon excitation of the fluorophore, the wavelength of the excitation source is shifted to a differing wavelength (e.g., a Stokes-shift) as it is emitted by the fluorophore. The emitted light is then detected and utilized to reconstruct a digital image of the target area, which can exhibit a differential in fluorophore concentration from surrounding tissues (e.g., fluorophore take-up). The digital image can be employed to provide functional characteristics about the inclusion, such as vascular endothelial growth factor (VEGF) conjugated with a dye fluorophore. However, FDOT methods have exhibited less than desirable reconstruction accuracy due to imperfect uptake of the fluorophore and background fluorophore noise.
While diffusive optical tomography provides benefits over alternative imaging methods, they suffer from drawbacks. Each of these imaging methods is confronted with challenges that impede widespread acceptance and implementation. One of the drawbacks is that the accuracy of reconstructed hemoglobin concentration and oxygen saturation is low without location information about the inclusion. It is therefore desirable to develop methods that can provide structural and functional characteristics about inclusions while at the same time facilitating accuracy in inclusion location so that accurate information about hemoglobin concentration and oxygen saturation can be obtained.